Various cards, for example, telephone cards, when sold at a store, cannot be overlapped because patterns on the cards must be visible, whereby it requires a large space to display them in a plane.
Also, there is the problem in that the telephone cards, when carried or collected to be held, take much time to select the kind or pattern of the card when overlapped.
Furthermore, when a person carries the cards, the person usually puts them in a pocket or purse or commutation ticket holder, but the cards are entirely contained in the pocket, thereby creating the problem in that the card is hard to be smoothly slipped in or out of the pocket.